


Slayer of Interest

by Jedi Buttercup (jedibuttercup)



Category: Buffy the Vampire Slayer, Person of Interest (TV)
Genre: Crossover, Gen, Gift Fic, Remixed, Surveillance, Wordcount: 1.000-5.000
Language: English
Status: Completed
Published: 2012-12-10
Updated: 2014-12-12
Packaged: 2017-11-20 19:54:32
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 3,300
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/589070
Author URL: https://archiveofourown.org/users/jedibuttercup/pseuds/Jedi%20Buttercup
Summary: <blockquote class="userstuff">
              <p>The Machine had kept giving Finch social security numbers from California. Week after week, the same little town.</p>
            </blockquote>





	1. Chapter 1

**Author's Note:**

  * For [beckyh2112](https://archiveofourown.org/users/beckyh2112/gifts), [kerrykhat](https://archiveofourown.org/users/kerrykhat/gifts).



> The prompt was the summary. Set Season 2-ish for Person of Interest; post-Chosen for Buffy.

In the early phases of the Machine, before Finch was ready to test it on current data, he'd calibrated it with examples from past records. Data gathered from before the modern, highly digitized age were often incomplete, but still of use in building predictive models, and by asking it to target specific moments he knew he could check the results against what had actually happened thereafter.

He hadn't restricted the output by geographical location, then, or by any differentiation in relevance. What had mattered was that it was _correct_ , and that the results were verifiable.

The project had been productive enough to be of considerable use in shaping his algorithms. However--there had been a few anomalies in the data, ones Finch had never been able to explain. He'd told Reese, once, about the numbers he'd seen come up again and again before they worked together, and how he'd finally realized it meant the victims were living with the person who would eventually kill them. But he'd thought it a mistake at first-- and part of the _reason_ he'd thought it was a mistake was because of one of those peculiar inconsistencies in the past predictive data.

The Machine had kept giving him social security numbers from California. Week after week, the same little town. A constant background trickle of numbers from the earliest data to which it had access, accelerating into a veritable storm in 1997 or so, and continuing through to the town's eventual collapse in May of 2003. It had occurred to him to check whether or not the Machine might have somehow realized the collapse was coming, perhaps from seismic data, and had been flagging numbers by their likelihood to be near the epicenter when it eventually happened; but even that had not panned out. Surprisingly few residents had still been within the town limits when the sinkhole swallowed it whole.

Many of those numbers had been repetitions. And a very specific subset of _those_ had shown up on an extremely regular basis, flagged at least once a week for the entire period between the upswing in activity and its unavoidable cessation. He'd never understood it; he had never seen another pattern like it anywhere else in the country. And curiously enough, though a high percentage of the repetitive numbers had in fact escaped Sunnydale alive, he had not seen any of them again, not then and not since he'd turned the Machine over to the NSA's care.

Not until that very morning, at least. Finch wrote the newest number on a slip of paper in a shaky hand, able to translate the code generated by the Irrelevant List without even bothering to look it up. It was the Most Frequent Number herself: one Buffy Summers.

She was there. She was _still alive_ , and she was _there_.

Finch felt curiously lightheaded, staring at her social security ID written out in his hand. He could almost taste the ozone in the back of his throat from those long, frustrating days manipulating code; could almost feel the throttling despair of watching names like Jessica Arndt's come up again and again and wondering if _this_ would be the time her abuser killed her. It felt like a second chance reclaimed; like the solution to an old mystery fluttering unexpectedly back into his grasp.

And, of course, a chance to save a life that had been-- apparently-- endangered so many times already, more than anyone should have to endure. Ms. Summers was barely thirty, even now! If he could only conclusively pinpoint what had threatened her, whether it be some unrecognized environmental factor or extreme gang violence, it would increase their chances of saving someone in like circumstance in the future.

He was deep into refreshing himself on her life story by the time Mr. Reese arrived at the library with a cup of tea and a box of pastries, smiling faintly as he taped a picture of a dark-haired young woman to the pane of glass they used as a case board. Another Sunnydale survivor to check off against the list he'd never quite forgotten.

"Pretty girl, Finch," Reese said, looming up behind him to brush a finger against the photo. Then he touched the one next to it, of a slightly older blonde in casual businesswear with a no-nonsense hairstyle, and his amused expression faded into a light frown. "Her, too. Which one's our number?"

Finch gestured to the blonde, then at the legend above it. "Buffy Summers. An executive with an international organization based in Britain known as the ISWC; she travels extensively and just arrived in New York this morning. I did find a few less ambiguous, but no less inexplicable references to an International Slayers and Watchers Council; presumably, like KFC Corporation, the current company shed the original name but kept the acronym for recognition purposes."

Reese raised his eyebrows. "You mean it's _not_ Kentucky Fried Chicken anymore?"

"Not since 1991, in fact, although the company still occasionally references the older name for advertising purposes," Finch informed him dryly. Then he continued. "The second young woman is Buffy's younger sister, and presumably the reason for her being in town: Dawn Summers is pursuing a graduate degree in linguistics at Columbia University."

"Huh. Sibling rivalry, maybe?" Reese mused, glancing between the photos again. "Anything going on in Dawn's life that her sister might have reason to be jealous of?"

Finch had been so accustomed to thinking of Buffy Summers as a recurrent victim that the suspicion in Reese's voice caught him entirely off guard. Dawn's number had appeared less frequently than her sister's in the Sunnydale Anomaly reports, and then only during the last three years of its existence. "You think the elder Ms. Summers is the perpetrator?"

Reese blinked at him, apparently equally surprised. "You don't?" he said, then gestured back to the board. "Look at her eyes, Finch; her stance. How recent is this picture?"

"A few months old, why?" he replied, studying the image with a furrowed brow. It looked no different to him than it had when he'd put it up, or than any of the other photos of her he'd seen, though of course she no longer wore revealing teenage fashions. But she'd always dressed as well as she could afford and carried herself with a certain strength that had caused him much consternation. What was Reese seeing that he had not?

"She looks-- familiar, somehow," Reese frowned. "But I think it's more her body language than anything specific to her. She's had training of some kind; I'm sure of it. And she's seen more than you'd expect in someone with her age and a corporate occupation. This ISWC aren't mercenaries, are they?"

"Not as far as I can tell. They read as a historical association primarily concerned with the acquisition, cataloguing, and translation of artefacts and documents of all types." Finch shrugged. "The younger Ms. Summers is also working there part time while she finishes her education."

"Any boyfriends or husbands in the picture?"

"One; Dawn Summers is currently engaged to a young man who attended high school with her sister. However!" He raised a finger as Reese's expression lit with interest. "The engagement is one of many months' standing, and I can find no record that Mr. Alexander Harris was ever romantically linked with Buffy Summers in any way. That's not conclusive, I realize; but she would have had plenty of opportunities to act before if the relationship was objectionable to her."

He lifted another photo and taped it into place beside Dawn, then linked the two with a swipe of erasable red marker. He seemed a reasonably healthy, reasonably good looking individual; though he did have one rather... unfortunate feature.

Reese snorted at the image. "Maybe she did. When did he lose the eye?"

Finch shook his head. "In 2003. Just before their entire hometown fell into a sinkhole. All hospital records of the incident were lost, but a fragmentary police report remains, claiming that it was the work of a religiously-motivated serial killer named Caleb Pardy."

Reese grimaced. "So this isn't these girls' first brush with violence."

Finch swallowed at that. "Far from it, I'm afraid," he said, touching Buffy's image again. But he only shook his head when Reese threw him a glance for clarification.

"This is her sister's address," he said, gesturing to the number and street name written under her face. "She's staying there for the duration of her visit."

Reese glanced at the address indicated, then nodded. "I'll check it out. Let me know if you find anything else relevant."

"Of course," Finch agreed. Then he turned back to the computer and opened up a new window.

_If the two of you are here, then where are the others?_ he asked himself. _Are you one of the Slayers of the old title? Or does someone mean to slay **you**?_

This time, he would not be satisfied with allowing his questions to go unanswered.


	2. Chapter 2

The first few hours Reese spent surveilling the new Number largely reinforced the guarded impression he'd picked up from her photo. He tracked Buffy Summers and her sister to a dinner meeting with a high-priced lawyer in an upscale restaurant, then settled in to watch from a distant table after his attempts to clone their phones failed. Every line of the blonde woman's posture spoke of restrained aggression and self-assurance; it gave him unsettling flashbacks to sitting silently next to Kara Stanton in meetings.

Compared to the more relaxed Dawn Summers, or even the legal barracuda they were chatting with over fancy salads and glasses of the house white blend, Buffy stood out like a cheetah next to a pair of house cats. Watching the way she handled the bread knife and shared tight, tooth-baring smiles with the woman across from her, he couldn't fathom why Finch had touched her picture with such reverence. Dawn, with her warmer expressions, ink stained fingertips, and much less militant posture, seemed a far likelier candidate for protection.

Still, it wouldn't be the first time that the situation was other than as it appeared. And Harold usually had his reasons for reacting as he did. So he'd try to keep an open mind until something definitive happened. And in the meantime... he didn't want to trip the trained instincts Buffy obviously had. Reese dropped his napkin and a hundred dollar bill on his plate as the lawyer stiffed the Summers women with _her_ check, then followed her out, trying the clone app again as he passed her. If they couldn't listen in on Buffy directly, they could at least overhear whatever report the lawyer might make about the meeting. Then he headed for a bench to blend in while he waited for his target to emerge.

"Any idea how the lawyer fits into this, Finch?" he asked the air, carefully tapping at his smart phone as if playing one of the popular game apps. He actually did have a respectable run going on Whirly Word, an anagram-solving game Finch had set up to camouflage the surveillance apps if he swiped his thumb just _so_ , but given how often he discarded, destroyed, or otherwise replaced his phone in any given month, it wasn't worth trying to fake enthusiasm for any of the ubiquitous score-tracking games.

" _Not in detail, I'm afraid_ ," Finch replied. " _The data on her phone is quite heavily encrypted. But the pattern of that encryption reveals something worrisome on its own: she's an employee of Wolfram and Hart. I've encountered the firm before, and never under pleasant circumstances._ "

Reese's mood soured further. Wolfram and Hart? He'd run across them once or twice during his time with the CIA as well, and _those_ had never been pleasant encounters, either. If the Number was a colleague of theirs, it was another point against her; but given the way the women had interacted, he'd bet against it. "I'd feel better about that if I'd been able to clone Ms. Summers' phone, or her sister's; they're definitely hiding something as well."

Finch paused, then added, as though it hurt him to admit it: " _Perhaps you were right to caution me about my assumptions. I'm afraid-- I'm afraid I've seen her Number before, quite frequently in fact_."

The implications of that admission hung in the air between them, unspoken. Reese remembered their conversation about Jessica vividly; and Finch's previous comment that this was far from the girls' first brush with violence. "So... you think there's something larger at work here. A history of threats. Her sister....?"

" _Yes; and several of their close friends as well. The Machine currently limits its output to Numbers for which intervention is physically possible; so I don't know if the pattern changed after Sunnydale collapsed. Their group has scattered across the globe in recent years. But when I tested the Machine on historic data, not limiting it by geographical relevance... for seven years, at least one of that small group appeared on the list on a near-weekly basis. Sometimes it would seem to calm; over the course of more than one summer, in fact, I saw no mention of Ms. Summers until the school year resumed. But even when she was not featured, her friends still appeared on the list on a discomfortingly regular basis. Unfortunately, I was never able to determine the precise nature of the threat._ "

Even given the destruction of the town, that was worrying. _Some_ type of record had to exist in order for the Machine to have made a prediction. But that data was unlikely to be in official, accessible databases, if Finch had been unable to reproduce the research it had used to make the determination. If it had been gang warfare or something similar there should have been records with at least one law enforcement agency, or mentions in newspapers; and at least some of those should have been accessible elsewhere even after Sunnydale collapsed into the sinkhole.

He thought of the acronym Finch had mentioned again-- _Slayers and Watchers?_ \-- and wondered.

"They're leaving the restaurant," he murmured, watching the women through down-turned eyelashes as they strode by. The elder Summers walked with sharp, angry strides, three hundred dollar heels clicking loudly on the pavement; the younger had a long-suffering expression on her face as she hurried to keep up.

"...can't _believe_ she thought we'd actually fall for that." Buffy's voice was as crisp as the lines of her short skirt and power-red blouse.

Her sister sighed, shaking her head in reply. "She didn't. Someone told her to make the offer; she made it the way she did because she knew it would piss you off. She's the one Faith told us about, remember? Even if Angel's gone, I bet...."

Their voices faded out of range, into the background hum of passersby, and Reese frowned. More names for Finch to research; more hints that the Summers women and Wolfram and Hart were opposed. But why were they on the same playing field to begin with?

He checked his watch and tucked away his phone, then set off after them, following along at half a block's distance. It was difficult to be unobtrusive about it at the speed they were walking, but fortunately, there was still plenty of foot traffic to blend in with. Night had fallen while the women were eating, but it wasn't yet late enough for the nine to five crowd to turn in. 

They'd taken the subway from Dawn's apartment, though, and retracing those steps required a little more subterfuge. Reese was the better part of two blocks away by the time they reached their destination, on much less sparsely populated streets... too far away to immediately intervene when three thugs stepped out of the shadows and advanced on the women.

It was difficult to tell whether they were carrying weapons at that distance. Their body language didn't suggest it, but Reese wasn't going to take any chances of losing the Number before they'd even determined what was going on. Particularly given how personally Finch was taking this one. He drew his handgun, hurrying to reach effective range--

\--then stopped short as Buffy turned toward the attackers, blocking his aim as she pulled some sort of dark, blunt blade from her purse.

His instincts hadn't been wrong: she was deadly poetry in motion, ducking the thugs' attempts to grab hold of her and shoving her sister to safety behind her. Then she lifted the blade and jabbed firmly at the chest of one, simultaneously leaning to kick the one trying to circle around her, and used the backswing of the stabbing motion to impale the third. Both stricken thugs bent forward over their wounds... then _crumbled_ , seeming to turn into ash. Grey particulate rained down on the sidewalk as though they'd been flash-cremated without burning anything else around them.

...Well. No wonder Finch had had difficulty tracking the threat.

Reese shook off his surprise, then put a bullet in the knee of the second thug as he-- it?-- recovered from being kicked and lunged for Buffy's back. Her sister screamed, flinching at the sound; Buffy followed through first, whirling to plunge her blade-- stake?-- into the assailant's chest before turning to stare in Reese's direction. Abandoned, the thug collapsed just as the others had, then disintegrated.

Threat eliminated, Reese made a show of turning the gun away and dropping it to the pavement as Buffy stalked toward him. Then he tapped the Bluetooth in his ear.

"Finch?" He cleared his throat. "What are your thoughts on the subject of vampires?"

" _Vampires? The popular mythic beings that subsist by feeding on the life essence of living creatures? I didn't take you for a Twilight fan, Mr. Reese._ "

"Think less Edward Cullen, and more something a secret organization might have been founded to 'slay'," he replied dryly, as Buffy finally reached his position.

"Hasn't Wolfram and Hart bothered me enough for one day?" the young woman accused him, green eyes flashing at him as though she could take him just as easily as she'd taken down her other foes. "What, did you think I'd fall all over you in gratitude for that? I don't appreciate stalkers, and I _don't like guns_."

"What a coincidence," Reese said, dryly. "Neither do I. I'm just really good at using them. Much as you appear to be with your weapon." He nodded to the item still clutched in her hand, clearly carved from wood now that he was close enough for a good look.

She seemed taken aback at that. "My... weapon?" she said, glancing at the stake as though it might have turned to something else in her hand while she wasn't looking. "I'm a vampire slayer; it's kind of in the job description. As you should already know."

"Unless I'm not with Wolfram and Hart," he pointed out, reasonably. Then he nodded to both women as Dawn Summers reached her sister. "Ms. Summers, Ms. Summers; my name is Reese. I had...."

Finch murmured suddenly in his ear: " _a premonition_...."

"A premonition," Reese repeated, "that you might be in danger."

When in doubt, use the language of the medium? 

Eyebrows flew up on both women; then they glanced at each other.

"Must be a Tuesday," Dawn quipped, stepping out from behind her sister.

Buffy's stance relaxed, though her expression soured as she finally tucked the stake away. "Figures. I can't even visit my sister without a prophecy crawling out of the woodwork. What now?"

" _I think we shall have to invite them to the library, Mr. Reese,_ " Finch sighed. " _I can't even begin to fathom the nature of the threat without more information._ "

"I think," Reese agreed, spreading his hands wide, "we have a lot to talk about."

**Works inspired by this one:**

  * [Independent 22 - Tea and Oranges](https://archiveofourown.org/works/5382383) by [Aadler](https://archiveofourown.org/users/Aadler/pseuds/Aadler)




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